These hand warmer packs are quite amazing. They are about 3" x 2" and make a gentle heat for about 7 hours once they are taken out of their vacuum packaging. Ingredients: iron, water, cellulose, vermiculite, activated carbon, salt. I have trouble keeping my hands warm in the deep cold, but these little guys really help. I slip them between my woolen mitts and my lined leather mitts, and my hands are toasty for a long time.